s390: introduce DUMY opcode for special use.

src/s390/simulator-s390.cc

Index: src/s390/simulator-s390.cc
diff --git a/src/s390/simulator-s390.cc b/src/s390/simulator-s390.cc
index 74d37bc20aed8d629f0f26f6b0e5bb5a4fac3dc0..df4c02dfeb2d71f0099f9c51cfa0b1d8a7dcc3ce 100644
--- a/src/s390/simulator-s390.cc
+++ b/src/s390/simulator-s390.cc
@@ -743,6 +743,7 @@ void Simulator::EvalTableInit() {
     EvalTable[i] = &Simulator::Evaluate_Unknown;
   }
 
+  EvalTable[DUMY] = &Simulator::Evaluate_DUMY;
   EvalTable[BKPT] = &Simulator::Evaluate_BKPT;
   EvalTable[SPM] = &Simulator::Evaluate_SPM;
   EvalTable[BALR] = &Simulator::Evaluate_BALR;
@@ -6058,6 +6059,12 @@ int Simulator::Evaluate_Unknown(Instruction* instr) {
   return 0;
 }
 
+EVALUATE(DUMY) {
+  DCHECK_OPCODE(DUMY);
+  // dummy instruction does nothing.
+  return 6;
+}
+
 EVALUATE(CLR) {
   DCHECK_OPCODE(CLR);
   DECODE_RR_INSTRUCTION(r1, r2);